Hardware Hacking 81and squeezing the wire. Sometimes it helps to connect a large resistor (100kOhm
- 1mOhm) between the clock input pin (pin 10) and ground or + 9 volts to
stabilize the circuit when you are not touching it.
Some applications for oscillators
The oscillator circuits we’ve made have a number of applications beyond just
plugging into an amplifier and droning away
Clocks for toys
Sometimes you can use the output of a high frequency oscillator as a substitute
for the clock circuit in a toy. Breadboard an oscillator that runs too high to hear –
use a capacitor around 100 pf and a pot to adjust the speed. Connect the ground
of the toy (- battery point) to the ground on your oscillator (- battery bus.)
Disconnect the timing resistor of the toy and solder a jumper to each of the pads
at either end of the resistor. Plug one wire into the output point of the oscillator.
Does the toy run? You may need to disconnect and reconnect the batteries, and
adjust the oscillator speed with the pot. If it doesn’t work, try the lead from the
other resistor pad. If neither works try another toy or give up. But if it does
work you can proceed with applying all of our oscillator variations (gated,
divided, etc.) to modifying the toy’s performance.
Crickets
Although a CMOS oscillator does not put out enough current to power an
ordinary loudspeaker (even a small one) directly, it will make beautiful cricket-
like sounds when wired to a Piezo disk. Connect the oscillator’s output to the
hot wire of a disk (center), and connect the ground to the circuit’s ground bus
(don’t use the Chapter 8 transformer in this configuration.) Low frequency
pulses should yield a pleasing clicking sound, while audio pitch should buzz like
a sultry August (in the Northern Hemisphere) afternoon. If they’re too quiet for
your taste, clamp the Piezo to a cookie sheet, or place it on a wooden matchbox
with a stone on top, or glue it to the wing of a balsa glider. Many of Felix Hess’
beautiful insect-like installations have been based on low-power circuitry
pinging Piezos.
More Randomness
Once you get the hang of these basic oscillator circuits and the way they are
supposed to work, don’t be afraid to experiment with alternate configurations,
even if you have no idea what you’re doing (see Rule 16) – these chips are hard
to blow up. The 74C14 and 4093 IC packages contain several identical oscillator
building blocks. Create multiple feedback paths by linking the outputs of some
oscillators to the inputs of others. Add multiple electrode touch contacts. You